KR20150004118U - Portable electronic device thermal management system - Google Patents

Abstract

An electronic device having a heat source arranged in a straight alignment with the battery of the device and a thermal management system in thermal contact with the heat source. The thermal management system may extend from at least the first surface of the battery to the second surface of the battery. The second surface of the battery may be adjacent to the heat dissipating element. The thermal management system may further be in thermal contact with the heat dissipating element. In addition, a portion of the thermal management system extends along the first and second surfaces of the battery and has an anisotropic ratio high enough to avoid transfer of heat to the battery to the extent that it disables the function of the battery.

Description

[0001] PORTABLE ELECTRONIC DEVICE THERMAL MANAGEMENT SYSTEM [0002]

This application claims the benefit of U.S. Provisional Application No. 61 / 777,612, entitled Portable Electronic Device Thermal Management System, entitled " Portable Electronic Device Thermal Management System, " filed March 12, This application claims the benefit of the priority of this application, the benefit of which is hereby incorporated by reference herein.

The disclosed embodiments relate to a thermal management system for a device including a portable electronic device, particularly a current generation battery or a next generation battery.

Ever since the invention of portable transistor radio, has been interested in portable (now called "mobile") electronic devices. This interest began with AM radio, which can be carried around by people, and continued with a camera and cassette tape player radio (eg, Walkman® Radio), and now cameras, mobile phones, mobile computers, tablets, MP- Player, and other devices.

As portable / mobile devices evolved over decades, the demands and capabilities of these devices have also evolved. In each generation of devices, devices can provide more of their content to their users in a more user-friendly format at a higher bandwidth than ever, as well as allow users to create, modify, and deliver content from their devices I have. As the convenience of these devices has improved, not only the power requirements for the devices have increased, but also the technology associated with the battery of these devices has improved. These current generation devices contain more energy, generate more power, and result in more heat. In addition to the battery, the hardware items of the devices (e.g., radio, display, and processing unit) have also become more powerful and have also caused additional thermal problems for these devices.

In addition, as these devices become more powerful, the tendency for these devices is smaller, lighter, thinner, higher in density of components inside the device, or different . The combination of increased power and reduced internal space of the components inside the device makes the thermal management of the system a factor that designers of mobile devices should consider and is a major consideration for almost all aspects of the design of high power portable devices And, in some cases, became a limiting factor.

Embodiments disclosed herein include an electronic device having a heat source arranged in direct alignment with the battery of the device and a thermal management system in thermal contact with the heat source. The thermal management system may extend from at least the first surface of the battery to the second surface of the battery. The second surface of the battery may optionally be adjacent to a heat dissipation element (e.g., a heat sink, heat pipe, chill plate, etc.). The thermal management system may further be in thermal contact with the heat dissipating element. In addition, a portion of the thermal management system extends along the first and second surfaces of the battery and has a sufficiently high spreading coefficient to avoid the formation of localized hot spots in any of the cells, And may be in thermal communication with the cells of the battery. In an alternative embodiment, the electronic device does not include such a thermal dissipation device.

It will be appreciated that both the foregoing general description and the following detailed description are provided to provide an understanding of the nature and characteristics of the present invention, as provided by the embodiments of the present disclosure and as claimed.

1 is an elevational plan view of a conventional configuration of a PCB and a battery.
Fig. 2 is a side view of the conventional configuration shown in Fig. 1. Fig.
3 is a perspective elevation view of a battery and thermal management system, in accordance with the present disclosure;
4 is a cross-sectional view taken along the line AA in Fig.
5 is a cross-sectional view of an alternative exemplary embodiment of a thermal management system.
6 is a cross-sectional view of an alternate exemplary embodiment of a thermal management system.
7 is a cross-sectional view of an alternate exemplary embodiment of a thermal management system.
Figure 8 is an elevation plan view of an internal configuration of a device including a thermal management system and a battery having one or more heat sources.
Figure 9 is a side view of the device of Figure 8;
Figure 10 is a side view of one embodiment disclosed herein.

The embodiments disclosed herein are applicable to a variety of mobile devices, such as, but not limited to, cellular telephones, notebook computers, netbooks, ultrabooks, laptops, tablets, MP-3 players, . These types of devices may be collectively referred to as mobile devices.

Some or all onboard wireless or cellular types (CDMA, GSM, WCDMA / UMTS, and LTE, and its data counterparts: Wi-Fi, BT, GPS, NFC, EV-DO; EDGE, GPRS, HSDPA, HSUPA VOIP) A battery, a central processing unit (CPU), a graphics processing unit (GPU), a drive chip, a memory chip, an RF amplifier and transceiver, a DC / DC switcher, a buck and / High power digital electronic devices (such as camera image processing and stabilization elements, static or video image illumination light sources), display elements (LEDs), power amplifiers, High-speed USB ports or other ports used for high-power applications such as those used to charge or operate peripheral devices (such as CD / DVD / Blu-ray drives), disk drives These mobile devices such as As the components in the devices become more powerful, the heat generated inside the device has also been found to increase. The aforementioned components are examples of heat sources.

The additional generated heat can have various adverse effects on the device. For example, in the case of a battery, applying an undesirable amount of heat to the battery can cause various failure mechanisms in the battery, such as changing the chemical reaction that occurs. Excessive battery heating by external components can also cause a reduction in the number of cycles that the battery can complete during its useful life, and will facilitate and increase the swelling of the battery, And further reduce the acceptability. In the worst case, excessive battery heating can increase the preference for undesirable irreversible reactions, which can lead to battery failure.

Concern over excessive heat exposure of the battery has led to fewer device design and layout options in the last three to five years. Recent devices with higher capabilities have placed batteries and PCBs in overlapping vertical configurations, often referred to as "battery-over-PCB" orientations, which may have been used prior to the introduction of 3G mobile communication technology. I never do that.

With respect to other types of components included in an electronic device, applying undesirable heat can result in a decrease in the operating frequency of the component and, consequently, in a reduction in the responsiveness of the entire device, The performance can be deteriorated. A further example of applying harmful heat can result in a reduction in the overall quality of the image on the display of the device.

Conventional attempts to solve the problem of transfer of an undesirable amount of heat from components of an electronic device to other components have been hampered by the fact that, for example, a battery generates an undesirable amount of heat, To offset or "offset" the desired components vertically and horizontally away from one another, such that they are not vertically aligned with the CPU or other components that can deliver them. Exemplary prior art device arrangements can be described with reference to Figure 1, which is a partial elevation view, and Figure 2, which is a partial side view. As can be seen, the battery 10 and the heat source 12 are arranged inside the electronic device with respect to the device housing 14. The battery 10 may be located in the lower left portion of the device and the heat source 12 (e.g., CPU) may be located in the upper right portion of the device. Thus, as illustrated in FIGS. 1 and 2, the battery 10 is vertically and horizontally offset from the heat source 12.

Embodiments in which two electronic components can be positioned, for example, in a direct thermal alignment, either horizontally or vertically with respect to each other, are disclosed herein. By way of example, each of the battery and the CPU may be located in the upper right portion of the device, the lower left portion of the device, or any other desired region of the device. In another embodiment, the battery and the CPU may be horizontally aligned. One embodiment disclosed herein includes an electronic device having a heat source arranged in a vertical alignment with a battery of an electronic device. In the previous sentence, the vertical alignment is used to mean that the battery and the heat source are not vertically offset from one another in the device.

The thermal management system may extend at least from the first surface of the battery to the second surface of the battery. Referring to Figures 3 and 4, in one embodiment, the first surface may be the upper surface 26 of the battery 20, which is generally rectangular, and the second surface may be a generally rectangular battery 20 And may be a side surface 28. In another embodiment, the first surface may be the upper surface 26 of the battery 20, which is generally rectangular, and the second surface may be the opposite lower surface 30 of the battery 20, which is generally rectangular. In other further embodiments, the first surface and the second surface may be any two surfaces on the generally opposite sides of the battery (whether rectangular, pocket-shaped or cylindrical). In another embodiment, the first surface and the second surface may be any two adjacent surfaces (e.g., an upper surface and a side surface). Alternatively, the present system may completely enclose the battery (e.g., the system may surround the upper portion 26, side 28 and lower portion 30 of the generally rectangular battery 20) Can be]. In other embodiments, the system may surround the entire circumference of the cylindrical battery. In addition, alternatively, the thermal system may substantially enclose the entire battery, thereby including only the openings necessary for electrical connection and / or to ensure adequate venting.

The device further includes that the thermal management system is in thermal contact with the heat source. When arranged in the device, the second surface of the battery may be adjacent to the optional heat dissipating element, and the first surface may be adjacent to the heat source. Exemplary heat dissipating elements include heat sinks, heat pipes, cooling plates, and the like. In this way, heat can be directed from the heat source to the heat dissipation element at the battery location. The heat dissipating element may be spaced from the case of the device; Such a case includes the outer surface of the device. Thermal contact is defined herein as including at least the heat source transferring heat to the thermal management system. In addition, a portion of the thermal management system extending along the first and second surfaces of the battery has a sufficiently high diffusion coefficient to avoid transfer of heat to the battery, which will create a local superheat point in a particular battery of the battery And can be in thermal communication with a plurality of battery cells of the battery. This local overheating point will cause the battery to be inhibited from operating. In one example of a local superheat point, one cell is hotter than the adjacent cell (s) by up to 10 ° C. In another example of a local superheat point, one cell is hotter than the adjacent cell (s) by at least 5 ° C. Examples of undesired heat that do not reach the battery include controlling the battery chemistry that causes the amount of heat to cause an irreversible reaction at an undesirable frequency; Raising the temperature of the battery beyond the threshold to such an extent that the rate at which the battery charges or discharges electricity is reduced to an undesirable level; Or reaching a temperature at which the battery excessively reduces the battery cycle life. In addition, it is desirable that the amount of heat delivered to the battery is suitable for battery technology, specifications and operating conditions in all cases, including safety tolerances under fault conditions.

In many cases, the conditions occur in a particular battery of the battery and can lead to premature failure of that particular battery. This can have a domino effect on other cells in the battery and can lead to undesirable performance of the battery. The local superheat point formed in the initial cell may be the cause of premature failure of the initial cell. The thermal management system can balance heat across a plurality of cells constituting the battery, thereby eliminating the hot spot in the initial cell.

Examples of types of batteries that may be applicable to the embodiment include a nickel-cadmium battery, a lithium ion battery, or a lithium polymer battery. The embodiments can also be applied to next-generation batteries as well. In addition, the embodiments are applicable to removable batteries or non-removable batteries. The detachable battery may be detached from the device without damaging any of the electronic device and / or other components included in the device.

Preferably, neither the battery nor the thermal management system is in contact with the outer surface of the device. Preferably, there is a gap between the battery and the outer surface of the device. It is also desirable that the thermal management system does not extend to the outer surface of the device. In addition, it is desirable that the thermal management system is not in thermal communication with the outer surface of the device.

Exemplary embodiments of the heat dissipation element may include one or more of an inner frame or a chassis, a cooling plate, a heat pipe, or a group of heat sinks selected from a device. Any of the heat dissipation elements mentioned may be comprised of any suitable plastic, metal, or other suitable material or combination thereof.

In certain embodiments, a portion of the thermal management system extending around the battery includes a flexible graphite sheet. Advantageously, the flexible graphite sheet in the thermal management system is a continuous sheet. In one embodiment, the flexible graphite is a sheet of compressed peeled graphite particles. Preferably, the anisotropic ratio of the flexible graphite sheet is at least greater than about 40, and other examples of suitable anisotropic ratios include at least about 75, at least about 100, and at least about 150. Anisotropy ratios are used herein to refer to the in-plane thermal conductivity divided by the planar thermal conductivity (thru-plane thermal conductivity). Graftech International Holdings Inc. The GrafTech International Holdings Inc. eGraf® heat spreader solution is an example of a sheet of compressed peeled graphite particles as described above. Another example of a flexible graphite sheet is the eGraf® SS1500 heat spreader, which is a graphitized polyimide.

One example of how such sheet of peelable graphite can be produced is U.S. Patent No. 3404061, the entirety of which is incorporated herein. An exemplary thickness of the sheet includes at least about 40 micrometers, at least about 50 micrometers, at least about 100 micrometers, and at least about 250 micrometers. With respect to thickness, there is no limit to the tolerable thickness of the sheet formed and surrounded by the battery. However, given the trend in electronic devices, it is hard to imagine that such devices will be designed to accommodate sheets with thicknesses greater than 2 mm. An example of how a graphitized polyimide sheet can be prepared is U.S. Patent No. 5091025, which is incorporated herein by reference in its entirety.

In view of the through thermal impedance, the graphite sheet is preferably at least 0.25 cm ² K / W, preferably at least 0.30 cm ² K / W, more preferably at least 0.40 cm ² K / W, It is advantageous to have a through thermal impedance of at least 0.50 cm < ² > K / W. Thermal impedance is a measure of material resistance to the transfer of heat through the body of a material. This is determined by multiplying the plane through thermal conductivity by the thickness of the graphite sheet.

With respect to the fractional coefficient of thermal diffusivity, the preferred diffusion coefficient is at least 0.040 W / K, more preferably at least 0.050 W / K, and even more preferably at least 0.060 W / K. The diffusion coefficient is a measure of how well a material equilibrates its exposed heat across its surface. The diffusion coefficient can be determined by multiplying the in-plane thermal conductivity of the flexible graphite sheet that constitutes a portion by its thickness. The flexible graphite sheet, which constitutes a part, covers most of the thermal management system; And may extend substantially over substantially all of the thermal management system.

In another alternative embodiment, the flexible graphite is a sheet and a polymer layer of graphitized polyimide resin, the polymer layer has a planar thermal conductivity of less than about 1 W / mK and a thickness of at least about 10 micrometers. Although not necessarily, the graphitized polyimide generally has a thickness of less than about 70 micrometers. An example of a graphitized polyimide product is Graftt International Holdings Inc. This includes the Graf® SS1500 solution.

Either one of the aforementioned graphite sheets is preferably free of elastomer in the sheet when used in a thermal management system. One or both of the major surfaces of the sheet may or may not be coated with a protective layer (typically a thermoplastic polymer layer such as a PET film). It is also possible that the main surface of the graphite sheet, which is not coated with the protective layer immediately above the main surface of the graphite sheet, has an adhesive layer on this main surface.

Optionally, the thermal management system may further include a second portion in thermal communication with the battery. The second portion may be located at a desired location on the battery to dissipate heat from the battery. For example, the second portion may be located at a known or perceived superheat point on the exterior of the battery. This second portion may be a thermal interface material, a heat spreader or other type of heat dissipation device. The second portion may also be in contact with the heat dissipating element or the second heat dissipating element.

Other optional embodiments may include a thermal insulating material, a dielectric or a shock absorbing material disposed between at least a second surface of the battery and a portion of the thermal management system extending along a second surface of the battery. In certain advantageous embodiments, the heat-insulating material, dielectricmaterial, or shock-absorbing material is disposed along both the first and second surfaces of the battery. In a further advantageous embodiment, the heat insulating material, dielectric material, or shock absorbing material is disposed along substantially all of the battery in which a portion of the thermal management system is located. Examples of such materials include various nonconductive polymer films and foams.

With reference now to Figure 4, the embodiments are further described. As can be seen, the battery assembly 50 includes a thermal management system 32 surrounding the battery 40. 4, the system 32 includes a sheet of flexible graphite 36 of either compressed, peeled graphite particles or graphitized polyimide disposed within the outer polymer layer 34. In one embodiment, And an inner polymer layer 38 disposed closest to the battery cell 40. The outer polymer layer 34 is a layer of polymeric material. Thus, as can be seen, according to this embodiment, the flexible graphite layer 36 is disposed between the outer polymer layer 34 and the inner polymer layer 38. It will be appreciated that the polymer layers 34 and 38 may alternatively or additionally be a dielectric or shock absorbing material. In addition, the inner polymer layer 38 may also function as an outer containment layer of the battery cell 40 containing electrochemical components. In addition, the outer polymer layer 34 may function as an attachment point or printing surface of the product label.

As previously described herein, the polymer layer / insulating layer / dielectric layer is optional, and likewise, the entire enclosure of the battery is optional. As such, various additional exemplary embodiments are now described with reference to Figures 5-7. As can be seen in FIG. 5, the thermal management system 32 includes an outer polymer layer 34 and a flexible graphite layer 36. In addition, the polymer layer 34 and the flexible graphite layer 36 are bonded only to the first side and the second side of the battery cell 40. As can be seen in FIG. 6, the thermal management system 32 includes a flexible graphite layer 36 and an inner polymer layer 38. The thermal management system surrounds not more than the entire battery cell 40 but more than three sides. A further exemplary embodiment is shown in FIG. 7, where the thermal management system 32 includes a flexible graphite layer 36 that surrounds the entire battery cell 40.

With reference now to Figures 8 and 9, in view of the above description, it will be appreciated that a heat source may be positioned in a straight alignment with the battery assembly 50, which includes the thermal management system 32, in either position A, . Positions A, B, and C are exemplary locations for a heat source and should not be used to limit the claims contained herein. A heat source at any of these locations may be in thermal contact with the thermal management system. Thus, for example, if the device comprises a heat source A, according to the above disclosure, the surface A 'is the first surface in thermal contact with the heat source, and the surface X is the surface of the battery (The outer surface 14 of the device). In other words, the first surface of the thermal management system 32 in thermal contact with the heat source A may be referred to as a first portion or portion of the thermal management system 32, But may be used for some and all of the other embodiments. Likewise, if the device includes heat source B, according to the above disclosure, surface B 'may be the first surface in thermal contact with the heat source and surface X may be the second surface. In addition, if the device comprises a heat source C, surface C 'would be the first surface in thermal contact, and surface X could be the second surface.

A further embodiment (denoted 100) is illustrated in FIG. As shown, the device 100 includes an outer surface 102. The heat source 104 and the printed circuit board 106 are inside the device. Battery 108 adjacent to and in thermal communication with source 104 is also shown. The thermal management system 110 is in thermal communication with the first side and the second side of the heat source 104 and the battery 108. In addition, voids are shown between the battery 108 and the outer surface 102, as well as between the system 110 and the outer surface 102. An exemplary embodiment of the system 110 is a heat spreader including an eGraf SS400 heat spreader (available from GrafTech, Pharma, Ohio, USA). Other embodiments of the system 110 may include combinations of one of Graffec's Graff® heat spreaders with Graftech's HiTherm thermal interface material.

In another particular embodiment, the thermal management system may be in physical contact with both the heat source and the battery.

In certain embodiments, a portion may comprise at least a portion of the label for the battery. In certain embodiments, a portion of the thermal management system may be included in a label for the battery. The label of the battery may serve to provide information or display purposes, electrical isolation benefits, and at least some amount of structural support.

Embodiments disclosed herein may be used to maintain the battery temperature within a desired range to prevent a negative impact on the battery, and preferably the battery is less than 95 캜, more preferably less than about 80 캜, Preferably less than about 70 < 0 > C, and even more preferably less than about 60 < 0 > C.

The embodiments disclosed herein may be used to enable the desired device design of the battery on the PCB. Other advantages of the embodiments disclosed herein include a reduction in the effect that the hot component can have on the battery, particularly when the hot component is adjacent the battery. This helps prevent localized heat build-up ("hot spots") on the battery from external sources, and thus makes it better to do thermal management of the battery only for the heat generated by the battery. In addition, the likelihood of any undesirable reaction caused by external heating is reduced. In addition, swelling of the battery, which can be caused by local external heating of the battery, is suppressed. In addition, with respect to operation of the battery, the embodiments disclosed herein may be used in conjunction with a thermal runaway caused by heating from a faulty component, such as when a faulty component is shorted or latched up. it is possible to provide an excellent safety margin from the runaway. A device comprising the embodiments disclosed herein may have a less expensive, thinner and / or more efficient design. A battery of a device including one of the embodiments disclosed herein will be less vulnerable to the formation of localized hot spots. In addition, the battery should exhibit a more uniform temperature profile. In addition, heat toward the battery will spread evenly over that portion of the battery, which is in thermal communication with the thermal management system.

The electronic device may not have an EMI shield around either or both of the heat source or the battery. In one particular embodiment, any EMI shield included in the device is not part of a thermal management system.

It is not necessary, but it is desirable that one or more of the embodiments disclosed herein allow the device to meet relevant EMC (Electromagnetic Compatibility) standards such as IEC standard 60601-1-2.

The above description is intended to enable a person skilled in the art to make the present invention. The above description is not intended to be exhaustive of all possible variations and modifications which will become apparent to those of ordinary skill in the art upon reading this description. However, it is intended that all such modifications and variations be included within the scope of the present invention as defined by the following claims.

Accordingly, while the specific embodiments disclosed herein have been described, these descriptions should not be construed as limiting the scope of the present invention except as set forth in the following claims. The various embodiments discussed above may be practiced in any combination thereof.

Claims (16)

As an electronic device,
a. A heat source arranged in direct alignment with the battery of the device,
b. A thermal management system in thermal contact with said heat source;
i. The thermal management system extending to at least a first surface of the battery,
c. A portion of the thermal management system extending along the first surface and the second surface of the battery, the portion being in thermal communication with a plurality of cells of the battery, Has a sufficiently high spreading coefficient to avoid generating localized hot spots to the extent that it disables the battery, and
d. Wherein the battery and the system
Lt; / RTI > 2. The electronic device of claim 1, wherein the battery comprises at least one selected from a nickel-cadmium battery, a lithium ion battery or a lithium polymer battery, and the heat source comprises an electronic component. 3. The electronic device of claim 2, wherein the second surface of the battery is adjacent to a heat dissipation element. 4. The electronic device of claim 3, wherein the heat dissipating element comprises at least one of a frame or a chassis of the device.   The electronic device of claim 1, wherein the portion comprises a sheet of compressed peeled graphite particles. The electronic device according to claim 1, wherein the battery can be removed without damaging the device. The electronic device of claim 1, wherein the thermal management system further comprises a second portion located in a desired location on the battery and in thermal communication with the battery to dissipate heat from the battery. 8. The electronic device of claim 7, wherein the second portion is in thermal contact with the heat dissipating element. 2. The electronic device of claim 1, further comprising a heat-insulating or dielectric material disposed between the battery and the portion. The electronic device according to claim 1, wherein there is no partition between the battery and the heat source. 2. The electronic device of claim 1, wherein the thermal management system is in physical contact with the heat source. 2. The method of claim 1, wherein the portion comprises a sheet and a polymer layer of graphitized polyimide resin, wherein the polymer layer has a through-plane thermal conductivity of less than about 1 W / Meter. ≪ / RTI > The electronic device of claim 1, wherein said portion comprises a sheet and a polymer layer of compressed peeled graphite particles, said polymer layer having a planar thermal conductivity of less than about 1 W / mK. The electronic device of claim 1, wherein the portion comprises at least a portion of a label for the battery. The electronic device of claim 1, wherein the portion is contained within a label for the battery. As an electronic device,
a. A heat source arranged in a straight alignment with the battery of the device,
b. A thermal management system in thermal contact with said heat source;
i. The thermal management system extending to at least a first surface of the battery,
c. A portion of the thermal management system extending along the first surface and the second surface of the battery, the portion being in thermal communication with a plurality of cells of the battery and having a diffusion coefficient of at least 0.04 W / K; and
d. Wherein the battery and the system
Lt; / RTI >

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